SciELO - Scientific Electronic Library Online

 
vol.47 número4ELECTROCHEMICAL BEHAVIOUR OF POLYPYRROL /POLYETHYLENGLYCOL COMPOSITESREACTIVITY OF[Mo(NHNPh2)(NNPh2)Br2(acac)] TOWARD-DI-IMINES: X-REY CRYSTAL STRUCTURE OF[Mo(NNPh2)2Br2(o-phen)] índice de autoresíndice de assuntospesquisa de artigos
Home Pagelista alfabética de periódicos  

Serviços Personalizados

Journal

Artigo

Indicadores

Links relacionados

Compartilhar


Boletín de la Sociedad Chilena de Química

versão impressa ISSN 0366-1644

Resumo

REYES, P. et al. Crotonaldehyde Hydrogenation on Rh/TiO2 catalysts: In situ DRIFTS studies. Bol. Soc. Chil. Quím. [online]. 2002, vol.47, n.4, pp.547-556. ISSN 0366-1644.  http://dx.doi.org/10.4067/S0366-16442002000400027.

The surface and catalytic properties in the vapor-phase hydrogenation of crotonaldehyde on Rh/TiO2 has been studied. It was found that a partial reduction of the support produces a surface decoration of the metal component. Thus, interfacial sites are created, which are responsible of an increase in the selectivity to crotyl alcohol, via enhancement of the polarization of the C=O bond. Photoelectron spectra revelead that rhodium is in different oxidation states, with a contribution of ca. 20 % Rhd + and 80 % Rhº species for LTR catalyst and only a slight increase of Rhd + for HTR catalyst. TEM studies revelead that Rh has metal particle size close 3 nm with small increases in the catalyst reduced at high temperature. DRIFTS essayed carried out under reaction conditions allowed to identify crotonaldehyde species strongly adsorbed through the C=C bond and weakly coordinated through both the C=C and C=O bonds. After reduction at 723 K an increase in the peak at 1660 cm-1 ascribed to an interaction between the carbonyl group and the surface, was observed. This peak seems to be stabilized at interfacial Rh/TiOx sites The deactivation in crotyl alcohol formation can be ascribed to the generation of strongly chemisorbed asymmetric carboxylate species detected by band at 1740 cm-1. This band grows at expense of crotonaldehyde O s - bonded intermediate chemisorbed on coordinatively unsaturated sites (Lewis acid sites) responsible of the crotyl alcohol obtaintion (detected by a band at 1653 cm-1). Additionally, a small band at 2068 cm-1 assigned to CO adsorbed on transition metals, which increases with time on-stream may explain the deactivation of the catalysts in flow systems.

Palavras-chave : Rh/TiO2; crotonaldehyde hydrogenation; DRIFTS.

        · resumo em Espanhol     · texto em Inglês

 

Creative Commons License Todo o conteúdo deste periódico, exceto onde está identificado, está licenciado sob uma Licença Creative Commons